1. Field of the Invention
The invention generally relates to a device capable of abating noise. More specifically, the device relates to reducing low frequency noise in an aquatic environment.
2. Description of the Relevant Art
Noise abatement techniques are often employed to satisfy environmental regulations, which are in place to protect marine life and habitat. For example, underwater acoustic noise from drilling ships in the Arctic is known to adversely affect the migratory patterns of marine mammals. Much of this noise occurs at low frequencies between 10 Hz and 200 Hz. Governmental environmental regulations related to underwater noise limit the oil exploration and drilling season in this region to a small fraction of the year. The current strategy for dealing with these regulations is a passive one in which biologists and other experts are employed by the oil companies to survey large areas in the vicinity of operations for these animals. Once their presence is detected, communications are sent back to the ship and operations are halted, making this strategy quite expensive and further reducing the amount of time spent exploring and drilling. Thus, there is an industry-wide need for an active noise abatement solution.
Underwater sound abatement technologies include either the use of freely rising bubbles or the deployment of air-filled, hard spherical shells. Systems that use freely rising gas bubbles generally require the continuous supply of compressed air, which in turn requires operation of an air compressor, thus consuming energy and also radiating its own noise. If the compressor is powered by a combustion engine, air pollution is created. Furthermore, air supply lines are typically run from the compressor to the location of deployment, thus increasing capital and deployment costs. Meanwhile, the use of air-filled, hard spherical shells has proven to be acoustically unsatisfactory for frequencies below 1000 Hz. Also, due to their physical dimensions, air-filled hard spherical shell systems are expensive to transport and deploy in the field.